Doping method, doping apparatus, and control system for doping apparatus

ABSTRACT

A doping method capable of controlling a dose amount in response to a change the ratio in ion species during a doping process, a control system for controlling a doping amount, and a doping apparatus having a control system are provided. An ion current value of a specific ion in an ion beam is measured. There is an ion detector that measures an ion current value of a specific ion in an ion beam and enters the obtained monitor signal into a control means. Set data for setting a predetermined dose amount is entered into the control means, convert data for obtaining an actual dose amount from the monitor signal is entered into the control means by a memory means. The control means performs data processing on the basis of the input monitor signal and the convert data, a control signal for obtaining the predetermined dose amount is entered from the control means to the dose amount control system to dope the controlled ion beam into the target material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ion doping apparatus and a dopingmethod using the same, and in particular, a high-precise ion dopingtechnology using impurity regions of source and drain regions of a thinfilm transistor (TFT), and so on.

2. Description of the Related Art

The technology for ionizing impurity elements used for the control ofvalency electrons of a semiconductor and accelerating the ionizedelectrons in the electric field for injection has been known as an ioninjection method. In late years, the doping has been performed byirradiating ions like a shower for injecting impurity elements into alarge area substrate of a liquid display device, a light emittingdevice, or the like.

The ion doping apparatus (hereinafter, also simply referred to as adoping apparatus) is designed such that a doping chamber is communicatedwith an ion source and is kept under vacuum while placing a substratetherein to subject the surface of the substrate to an ion currentirradiated from the ion source. The ion source comprises a plasmachamber, a lead accelerating electrode system for pulling out ionsgenerated in the plasma chamber, and a decelerating electrode system forcontrolling the influx of secondary electrons. In this case, a porouselectrode is generally used as an electrode, so that ions pass throughthe pores to form an ion current directing toward the doping chamber.

As a method for plasma generation in the ionic source, there are severalprocesses known in the art, such as a direct discharge system, a highfrequency discharge system, and a microwave discharge. In addition,plasma can be confined in the inside of the ion source by theapplication of an electric field. Alternatively, a cusp magnetic fieldmay be formed by arranging a permanent magnet around the plasma chamber.

In many cases, such a doping apparatus does not require a massseparation, so that all of ion species (positive charges) formed in theplasma chamber is accelerated in the electric field caused by the leadelectrodes and injected into the substrate. In many cases, material gas(diboron (B₂H₆) or phosphine (PH₃)) diluted with dilution gas such ashydrogen is used as a material of gas for the generation of ions. As aresult, in addition to the objected impurity ions (boron ions andphosphorus ions), a large amount of hydrogen ions is introduced at thesame time.

In the case of using diboron as material gas, ions such as H⁺, H₂ ⁺, H₃⁺, BH_(x) ⁺ (X: 1-3), B₂H_(y) ⁺ (y: 1-6) can be generated. The abundanceratio of these ion species depends on the dilution ratio of material gasand the conditions of plasma generation. When accelerating in theelectric field without mass separation, a plurality of these ion specieswill be irradiated on the substrate.

Concretely, a spectrum shown in FIG. 9 can be obtained by themeasurement with an EXB mass separator on each of ion species generatedat the time of using diboron gas diluted to 5% with hydrogen as materialgas. In this case, the peak of B₂H_(y) ⁺ ion is observed in the vicinityof a mass number of 20. Furthermore, the peak of H⁺ ion at a mass numberof 1 and the peak of H₃ ⁺ ion at a mass number of 3 are observed,respectively.

A faraday cup electrometer (FCE) is used as the doping apparatus andmonitors an ion current for adjusting the dose amount of the doping.However, the FCE measures only a current value based on the total ionsincluding diluted-gas ions generated from the diluted gas in addition tothe impurity ions such as phospine and diboron (used for the control ofvalency electrons) generated from the material gas. Therefore, there isa problem that the amount of impurity ions to be injected changes as theratio of the respective ions generated in the plasma chamber changes.

FIG. 10 is a graph that represents the distributions of elements (boron)with the respective mass numbers of 10 and 11 in an oxidative siliconmembrane in the depth direction, which is measured by a secondary ionmass spectrometer (SIMS) The figure shows the changes in concentrationat the time of sequentially doping a plurality of substrates using thedoping apparatus. In the data shown in the figure, the concentration ofboron increases as the number of the doping treatments increases (i.e.,the doping process proceeds in the later half) even though each dopingtreatment is set to the same dose amount. Therefore, the resultsindicate that the number of the doping treatments increases as the ratioof boron-containing ion species increases.

In addition, in FIG. 11, there is shown variations of threshold voltagesamong the substrates of TFTs prepared by performing the channel dopingunder the same conditions. In this case, also, it is observed that thethreshold voltage tends to shift to the plus side as the number ofdoping treatments increases (the number of substrates being processedwith doping increases). The results indicate that the amount ofintroduction of boron increases.

Furthermore, in one of the prior art documents (e.g., Japanese Laid-OpenPatent Application No. 2001-357813), there is a method for independentlymeasuring each of the ion species generated from the material gasincluding the diluted gas by polarizing and separating these ion specieswith a polarizer. Therefore, such a method allows the control of thedoping amount of each ion.

However, several problems have been found in the above processcomprising the steps of separating each ion, measuring the concentrationof the ion from a current value based on each ion to adjust the amountof the doping. For example, when the amount of the objective ion speciessuch as channel dope is low, the objective impurity ion cannot bedetected as the concentration thereof becomes lower than the lower limitof the detectable range.

SUMMARY OF THE INVENTION

For solving the above problems, it is an object of the present inventionto provide: an ion doping method that allows an ion doping apparatus toadjust the doping amount of ion species with a high degree of accuracysuch that the ion doping apparatus not only adjusts the amount of dopingwhen the ratio of ion species changes but also, in particular, correctlymeasures the ratio of ion species to be injected at lower concentration;a control system for adjusting the doping amount of ion species; and anion doping apparatus equipped with such a control system.

In the doping apparatus, the doping amount of the impurity ions (oneconductive type impurity ions) for the control of valency electrons canbe adjusted appropriately by measuring ions generated from the dilutedgas and specific ions generated from the material gas even though theratio of a plurality of ion species contained in the ions to be injectedhas changed in the process.

In the present invention, other than the ion containing one conductivetype impurity element, an ion (preferably, an ion having a highabundance ratio) except one of the impurity ions contained in thediluted gas and the material gas is used as the above specific ion to bemeasured, whereby it becomes possible to control the doping amount ofions that contains one conductive type impurity elements to be dopedeven in the case of channel dope where the concentration of the materialgas is low.

For instance, the amount of ions including boron to be generated fromthe dopant and injected is indirectly found on the basis of theconcentration of hydrogen ion obtained by performing the measurementwith EXB etc. on hydrogen ion to be generated from the diluted gas whenthe dopant is diboron and hydrogen is used as the diluted gas. Usingthis kind of the method, furthermore, it is possible to adjust thedoping amount even though the dilution rate of the material gas is high(i.e., the concentration of ions (boron) to be injected is low).

Here, in the case of the doping treatment using gas containinglow-concentrate diboron (B₂H₆) diluted with hydrogen, spectrums obtainedby the measurements with the EXB separator are shown in FIGS. 5A and 5B,respectively.

In FIGS. 5A and 5B, the current value of H₃ ⁺ and the current value ofH₂ ⁺, which are hydrogen ions generated from the dilution gas, aredetected while the current value of B₂H_(x) ⁺ derived from ion speciesthat contains impurity elements generated from the material gas is notdetected. This is because the density of diboron is very low but withinthe concentrations always required in the general channel dopingprocess.

In this way, the present invention is characterized in that theconcentration of ions containing impurities elements is indirectlydetected by using ions that do not contain impurities elements (ions notcontaining impurities elements generated from the material gas or thediluted gas) and that are sufficiently detectable in a mass analysiswhen the ions that contain impurity elements are hardly measured in adirect manner.

Specifically, it is characterized by indirectly detecting theconcentration of ions that contains boron using the current value of aspecific ion (e.g., the current value of H₃ ⁺) among the hydrogen ionspecies in which sufficient current values are being obtained in FIGS.5A and 5B without using the current value of B₂H_(x) ⁺ even when theimpurity ion is boron. For more accurately controlling the injectionamount of ions, it is preferable to measure the correlation date betweenthe current value of the specific ion (H₃ ⁺) measured by the EXBseparator and the concentration of the impurity ion (boron) obtained bythe SIMS analysis.

In addition, in the case of sequentially performing the doping treatmentdescribed above every time each of the substrates is processed, thecurrent value of the specific ion (H₃ ⁺) measured for each of thesubstrates using the EXB separator is shown in FIG. 6. In this figure,the lateral axis of the graph represents the number of the substratessequentially subjected to the doping treatment and the vertical axisthereof represents the current value of the specific ion (H₃ ⁺). Asshown in the figure, it is found that the current value of the specificion (H₃ ⁺) decreases as the number of the substrates being treatedincreases. Furthermore, each of the diluted gas and the material gascontains a fixed amount of the impurities (boron). Thus, it is foundthat the concentration of ion species that contains impurity elements(boron) increases as the number of substrates being treated increases.

In other words, the present invention is a method of conducting a dopingtreatment by measuring the amount of current of the specific ion withthe EXB separator just before the doping treatment and determining theconditions of a subsequent doping treatment. In addition, the presentinvention is a program to incorporate the results of the measurementinto the doping conditions. Furthermore, the present invention is adoping apparatus on which such a program is installed. The concentrationof the impurity elements can be made constant using the presentinvention. Therefore, a stable threshold voltage can be controlled.

Furthermore, an aspect of the present invention is a doping method inwhich a plurality of ion species that contain one conductive typeimpurity element is simultaneously injected into a target materialwithout conducting a mass separation, comprising the steps of: selectingan ion having the maximum abundance ratio among the plurality of ionspecies to measure an ion current of the selected ion; making acomparison between the ion current of the ion having the maximumabundance ratio and converted data associated with the concentration ofthe one conductive type impurity element; and adjusting the dose amountof the ion such that the concentration of the one conductive typeimpurity element to be injected into the target is made to be constant.

Another aspect of the present invention is a doping method in which aplurality of ion species that contain one conductive type impurityelement and a specific ion is simultaneously injected into a targetmaterial without conducting a mass separation, comprising the steps of:selecting a specific ion among the plurality of ions to measure an ioncurrent of the selected ion; making a comparison between the ion currentof the specific ion and converted data associated with the concentrationof the one conductive type impurity element; and adjusting the doseamount of the ion such that the concentration of the one conductive typeimpurity element to be injected into the target is made to be constant.

In each of the above aspects of the invention, the impurity element ofthe one conductive type may be boron, and the ion having the maximumabundance ratio may be a hydrogen ion.

Furthermore, the hydrogen ion may be one of H⁺, H₂ ⁺, and H₃ ⁺.

Another aspect of the present invention is a control system for a dopingapparatus, comprising: a dose amount control system having a means forgenerating a plurality of ions including an ion that contains a oneconductive type impurity element and a specific ion at a constant ratioand a means for generating an ion beam constructed of the plurality ofions; an ion detector for measuring the ion current value of the ionbeam and entering the obtained monitor signal into a control means; aninput means for entering set data for setting a predetermined doseamount into the control means; a memory means for entering a convertingdata for calculating an actual dose amount from the monitor signal intothe input means; and the control means for performing a data processingon the basis of the input monitor signal and the input convert data andentering a control signal for obtaining the predetermined does amountinto the dose amount control system, wherein an ion current value of thespecific ion contained in the ion beam is measured by the ion detectorhaving a mass separator.

Another aspect of the present invention is a control system for a dopingapparatus, comprising: a dose amount control system having a means forgenerating a plurality of ions including an ion that contains oneconductive type impurity element and another ion at a constant ratio anda means for generating an ion beam constructed of the plurality of ions;an ion detector for measuring the ion current value of the ion beam andentering the obtained monitor signal into a control means; an inputmeans for entering set data for setting a predetermined dose amount intothe control means; a memory means for entering a converting data forcalculating an actual dose amount from the monitor signal into thecontrol means; and the control means for performing a data processing onthe basis of the input monitor signal and the input convert data andentering a control signal for obtaining the predetermined dose amountinto the dose amount control system, wherein an ion current value of theion having the maximum abundance ratio in the ion beam is measured bythe ion detector having a mass separator.

Furthermore, in each of the above aspects, the ion detector may comprisea first ion detector for measuring a first ion current value on thebasis of the total ions included in the ion beam at a position where atarget material is placed and a second ion detector for measuring asecond ion current value on the basis of the total ions included in theion beam at a monitoring position.

A further aspect of the present invention is to a doping apparatuscomprising the above control system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for illustrating the doping method of thepresent invention;

FIG. 2 is a flow chart for illustrating the doping method of the presentinvention;

FIG. 3 is a flow chart for illustrating the doping method of the presentinvention;

FIG. 4 is a flow chart for illustrating the doping method of the presentinvention;

FIGS. 5A and 5B are diagrams showing the results obtained by the EXBmeasurement, where FIGS. 5A and 5B show the results obtained from thedifferent substrates, respectively;

FIG. 6 is a graph showing the results obtained by the EXB measurement;

FIG. 7 is a schematic explanation view for illustrating theconfiguration of the doping apparatus to be used in the presentinvention;

FIG. 8 is a schematic explanation view for illustrating theconfiguration of the doping apparatus to be used in the presentinvention;

FIG. 9 is a graph for illustrating the prior art;

FIG. 10 is a graph for illustrating the prior art; and

FIG. 11 is a graph for illustrating the prior art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiment 1

In a first embodiment of the present invention, we will describe amethod for controlling a dose amount in a doing device of the presentinvention with reference to FIG. 1 and FIG. 2. Here, the presentembodiment will describe the case in which low-concentrated boron isinjected using 1% B₂H₆ hydrogen-diluted gas with a very smallion-species ratio.

The doping apparatus of the present invention comprises a control systemconstituted of an ion detector 101 that detects the ion current of anion contained in an ion beam pulled out of an ion source, a controlmeans 102 where a monitor signal measured by the ion detector 101 isentered, an input means 103 for entering set data for setting a desireddose amount into a control means 102, a memory means 104 for storingdata (analytical curve) for converting the data measured by the iondetector to the dose amount in advance and entering the convert datainto the control means 102, a dose amount control system 105 forreceiving a control signal based on these input data from the controlmeans 102 as shown in FIG. 1.

The control signal entered from the control means 102 is responsible forcontrolling the parameters related to the control of dose amount (theamount of impurities). The parameters may include discharge conditions,acceleration voltage, the flow rates of material gas, diluted gas, orthe like, pressures, and so on.

Referring now to FIG. 2, the doping operation of the doping apparatusconstructed as described above will be described in detail.

First, the number of substrates to be introduced into the dopingapparatus and the amount of the impurities (the dose amount (set value))desired to be injected into each substrate are entered one by one. Then,the control means 102 read and incorporate these input data entered bythe input means 103. Here, the dose amount at this time is of containingthe total ions not only impurity ions but also other ions.

Subsequently, the ion detector 101 obtains a measuring value (ioncurrent value) at a processing position at which the substrate isarranged at the time of doping and a measuring value (ion current value)at a monitoring position. In addition, the ion electric current value atthe position where the substrate is arranged is the mean or median ofvalues provided by the measurements at different points. From thesevalues (the measuring value at the processing position and the measuringvalue at the monitoring position), the conversion value (α) can becalculated from the following formula (1).α=the measuring value at the processing position/the measuring value atthe monitoring position  (1)

Furthermore, the EXB measurement is performed for detecting a specificion. Concretely, the measurement is performed on a specific ion among aplurality of ions to be injected at the time of doping using an EXBseparation detector.

Here, the term “EXE separation detector” means an assembly prepared byattaching an ion detector for measuring an ion current on an EXBseparator. In addition, in the case of a low concentration as in thisembodiment, the current value of ion (B₂H_(y) ⁺) that contains impurity(boron) cannot be measured. Thus, H₃ ⁺ ion that allows the biggestelectric current is provided as a specific ion. Therefore, the currentvalue of the H₃ ⁺ ion will be then obtained. The measurement can beperformed during the step of replacing the treated substrate with newone or during the treatment.

Here, the concentration (C) of the impurity ion can be calculated fromthe current value of the specific iron using the analytical curve (thecorrelation data A between the impurity ion (B₂H_(y) ⁺) and the specificion (H₃ ⁺) using the SIMS analysis data) of the memory means 104 shownin FIG. 2. Furthermore, the data A should be measured before the dopingprocessing and stored in the memory means 104 in advance. Here, thecurrent value (a) of the specific iron to the target impurityconcentration (f(a)) and the impurity concentration (f(b)) to themeasured current value (B) of the specific ion are can be calculated,respectively.

Furthermore, the conversion value (β) can be calculated from thefollowing equation (2) on the basis of the target impurity concentration(f(a)) obtained from the data A, and the impurity concentration (f(b)).β=Impurity concentration (f(b))/Target impurity concentration(f(a))  (2)

Subsequently, the doping processing is initiated with a dose amount (D)entered from the input means 103 and read in the control means 102 atfirst.

Next, an ion current (i(t)) at the monitoring position is measured.Here, an ion detector used for the measurement of an ion current may beFaraday cup instrumentation. A dose amount (Q(t)) at the monitoringposition can be calculated with the following equation (3) from the ioncurrent value (i(t)) measured by the ion detector.Q(t)=∫(i(t)dt/q)  (3)(wherein q=elementary electrical charge)

Furthermore, the dose amount (Q(t)) obtained here and the conversionvalue (α,β) obtained in advance are used together in the equation (4) tocalculate the dose amount to the actual substrate (actual dose amount:d).Actual dose amount (d)=α×β×Q(t)  (4)

Here, the measured ion current value is entered in the control means 102and is then subjected to the data processing based on the equations (1)to (3), followed by being accumulated as new data (actual dose amount:d).

Then, the dose amount (D) entered from the input means 103 is comparedwith the data measured by the ion detector 101 and the actual doseamount (d) calculated on the conversion data entered from the memorymeans 104 at the control means 102. As a result, when the actual doseamount (D) reaches the target dose amount (d), the dose amount controlsystem 105 of the doping apparatus receives a signal from the controlmeans 102 to terminate the doping processing, so that the dopingprocessing on the substrate can be terminated. However, when the actualdose amount (d) does not reach to the target dose amount (D), the dopingprocessing is just continued. Subsequently, when it reaches to thetarget dose amount (D) at last, the processing on the substrate iscompleted. Here, the so-called dose amount control system 105 usedherein includes an ion source, a gas supply system, an electric sourcefor controlling these structural elements, and so on, which are relatedto the control of the dose amount to be doped in the target material,using their discharge conditions, acceleration voltage, flow rate,pressure, and so on as parameters.

When the doping of one substrate is completed, the next substrate is fedto the processing. Concretely, it is started again to measure the ioncurrent value at the processing positions. A method of processing iscarried out by the same way as that of the method previously described.In addition, the predetermined number N of the substrates is subjectedto the similar processing, repeatedly. A serious of the dopingprocessing is completed when the predetermined number N of thesubstrates are completed.

In the present invention, furthermore, the processing may be performedby the method shown in FIG. 3 instead of the method shown in FIG. 2.

Furthermore, after completing the doping processing on a sheet of thesubstrate, the doping processing on the subsequent substrate isinitiated again from the measurement of the current value of thespecific ion (H₃ ⁺) with the EXB measurement. The processing method isperformed by the same as one illustrated in FIG. 2. Similarly, a seriesof the doping processing is completed when the same processing isrepeated until the entire predetermined number N of the substrates isprocessed.

As described above, the impurity concentration is measured from thecurrent value of the measurable specific ion. In the method foradjusting the dose amount, there is an advantage of terminating in asort time because the measurement may be performed only around the peakof ion having a specific mass when the EXB measurement is desired to becompleted in the short time in consideration with throughput.

Embodiment 2

The method for controlling the dose amount is explained using FIG. 4. InEmbodiment 2, different from Embodiment 1, the impurity concentration tobe injected into the substrate is calculated from the current value ofthe specific ion obtained by the EXB measurement.

Here, the steps before obtaining the conversion value (α) are the sameas those of Embodiment 1, so that the explanation thereof will beomitted from the following description. However, the dose amount (D′) ofonly the impurity ions is entered through the input means 103 and isthen read and incorporated in the control means 102. In addition, thedose amount at this time is the dose amount of only impurity ions.

When the conversion value (α) is calculated, the doping processing isinitiated. Here, in Embodiment 2, a low-concentrated boron is injectedusing 1% B₂H₆ diluted gas with an extremely small ion-species ratio.

Next, the current value (i(t)) is measured by the EXB measurement. Themeasurement is performed during the processing with the ion detector 101equipped in the EXB measuring device.

Next, the doping is initiated under the predetermined conditions (e.g.,15 kV, 50 nA/cm²).

Subsequently, the ion detector 101 measures the current value (i(t)) ofthe specific ion at the monitoring position. Note that, furthermore, thecurrent value (g(i(t)) can be obtained by an analytical curve of thememory means 104 shown in FIG. 4 (the correlation data B between thecurrent value (j) of the impurity ion (B₂H_(y) ⁺) and the current value(i(t)) of the specific ion (H₃ ⁺) obtained by the SIMS analysis). Thedata B is measured before the doping processing. There is the need ofstoring the data B in the memory means 104 in advance.

Here, the current value (g(i(t)) of the impurity ion obtained iscalculated using the equation (3) described in Embodiment 1, so that thedose amount (Q′(t)) at the monitoring position can be obtained.

Furthermore, the dose amount (actual dose amount: d′) to the actual doseamount can be obtained using the following equation (5) with the doseamount (Q′(t)) obtained here and the conversion value (α) previouslyobtained.The actual dose amount (d′)=α×Q′(t)

Here, the measured ion current value is entered in the control means 102and is then subjected to the data processing based on the equations (3)to (5), followed by being accumulated as new data (actual dose amount:d′).

Then the dose amount (D′) entered from the input means 103 is comparedwith the data measured by the ion detector 101 and the actual doseamount (d′) calculated on the conversion data entered from the memorymeans 104 by the control means 102. As a result, when the actual doseamount (d′) reaches the target dose amount (D′), the dose amount controlsystem 105 of the doping apparatus receives a signal from the controlmeans 102 to terminate the doping processing. Thus, the dopingprocessing on the substrate can be terminated. However, when the actualdose amount (d′) does not reach to the target dose amount (D′), thedoping processing is just continued. Subsequently, when it reaches tothe target dose amount (D′) at last, the processing on the substrate iscompleted. Here, the so-called dose amount control system 105 usedherein includes an ion source, a gas supply system, an electric sourcefor controlling these structural elements, and so on, which are relatedto the control of the dose amount to be doped in the target material,using their discharge conditions, acceleration voltage, flow rate,pressure, and so on as parameters.

When the doping of one substrate is completed, the measurement of thecurrent value of a specific ion (H₃ ⁺) with the EXB measurement thereofis initiated again. A method of processing is carried out by the sameway as that of the method previously described. In addition, thepredetermined number N of the substrates is subjected to the similarprocessing, repeatedly. A serious of the doping processing is completedwhen the predetermined number N of the substrates is completed.

In addition, in Embodiment 1, the process may be performed as shown inFIG. 2. After completing the doping on one substrate, the dopingprocessing of the next substrate may be started from the measurement ofion current value at the processing position.

When the EXB measurement is performed during the processing inEmbodiment 1 or Embodiment 2, the EXB measuring device should bearranged on the outside of the processing substrate. However, in thecase of a substrate-scanning type injection device, the EXB measuringdevice may be mounted just below in the vicinity of the substrate (inthe case of the vertical ion source) or at the near of the substrate (inthe case of a vertical type ion source).

Embodiment 3

In Embodiment 3, we will describe one embodiment of the doping apparatusin accordance with the present invention.

A doping apparatus shown in FIG. 7 comprises an ion source 701, a dopingchamber 702 capable of arranging the substrate on the outlet of the ioncurrent thereof, a road lock chamber 703, a waiting chamber 704, and atransport chamber 705. These chambers 702-705 are communicated with gatebulbs. In addition, the transport chamber 705 has a transport meanshaving a double arm and other chambers are equipped with transport meansand substrate-holding means (not shown). In addition, an exhaust means708 allows the doping chamber 702, the transport chamber 705, thewaiting chamber 704, and so on become possible of vacuum exhausting. Theexhaust means 708 may be an appropriate combination of a dry pump, amechanical buster pump, a turbo molecular pump, and so on.

In the doping chamber 702, a substrate is held to perform an ion doping.In the case of processing the substrate having a surface area largerthan the opening of the ion flow, the ion doping processing can beperformed on the whole surface of the substrate by scanning with a stage707. In such a case, the cross section of the ion current may berectangle or linear to irradiate the substrate, so that there is no needof increasing the dimensions of the device. Furthermore, in FIG. 7, thesubstrate is arranged horizontally, and an ion beam is irradiated in thedirection perpendicular to the substrate. For reducing particles, thesubstrate may be arranged in a vertical direction so as to be irradiatedwith an ion beam in the direction.

Similar to the conventional ion source, for the purpose of controllingvalency electrons, the ion source 701 comprises a gas-supplying system719 for supplying material gas that contains impurity elements and afilament 711 for generating plasma. Here, but not shown in the figure,there is provided an anode corresponding to the filament provided as acathode. In the configuration of the doping apparatus shown in FIG. 7,there is shown the generation of plasma in the type of a directdischarge using the filament. However, the plasma may be generated usinga capacity coupling type antenna, an induction coupling type antenna, ora high-frequency type antenna may be adapted.

A drawer electrode system comprises a drawer electrode 712, anaccelerating electrode 713, an inhibitory electrode 714, and an earthelectrode 715. Each of these electrodes has a plurality of openings sothat ions are allowed to pass through these openings. Ions areaccelerated by the drawer electrode 712 on which a drawer voltage (Vex)is applied and the accelerating electrode 713 on which an acceleratingvoltage (Vac) is applied. In the inhibitory electrode 714, ions beingdispersed are corrected to increase the directionality of ion current.For instance, the acceleration of ions at energy of 10 to 100 keV isattained by shifting an acceleration voltage (Vac) with the applicationof a drawing voltage (Vex) of 1 to 20 kV.

The doping gas may be PH₃, B₂H₆, or the like, which is used at aconcentration of about 0.1 to 20% by diluting with hydrogen or inertgas. In the case of PH₃, PH_(x) ⁺, P2H_(x) ⁺, H_(x) ⁺, and so on aregenerated as ion species. When the mass separation is not performed,ions are accelerated by the drawer electrode system and introduced intothe doping chamber 702 in which the substrate is mounted. Ions arealmost linearly pulled out using four electrodes and are then irradiatedon the substrate.

Furthermore, in the doping chamber 702, an ion detector for measuringthe injected ion current value is installed. Concretely, there are anion detector 720 for measuring an ion current value at the monitoringposition, an ion detector 721 for measuring the processing position tomeasure the dose amount to be injected into an actual substrate, and anEXB separation detector 722. In addition, the EXB separation detector722 is designed as a combination of an EXB separator and an iondetector. Thus, the ion detector detects only the ion current valueseparated by the EXB separator.

Referring now to FIG. 8, there is shown the positional relationshipamong the ion detector 720 for measuring the ion current value at themonitoring position, the ion detector 721 for the measurement of aprocessing position, and the EXB separation detector 722, which arearranged in the doping chamber 702 shown in FIG. 7.

FIG. 8 is a top view of the substrate having the doping chamber 702shown in FIG. 7. The line X-X′ shown in FIG. 8 corresponds to the lineX-X′ shown in FIG. 7. In addition, the structural components shown inFIG. 8 are represented by the same reference numerals as those of FIG.7, so that these figures may be property made reference to each other.

In FIG. 8, the ion detector 720 for measuring the ion current value isarranged at the monitoring position such that the ion detector 720 isnot overlapped with the substrate 705 and the stage 707.

Furthermore, a plurality of the ion detectors is arranged on the middleof the substrate 705. In addition, the mean value or the median value ofthe ion current values measured by a plurality of the ion detectors willbe an ion current value at the processing position of the dopingapparatus of the present invention.

Furthermore, the method for arranging the ion detector for measuring theprocessing position measurement is not limited to the verticalarrangement shown in FIG. 8. Alternatively, it may be arranged in thehorizontal direction or may be arranged so as to be crossed in themiddle.

Furthermore, the EXB separation detector 722 is also positioned so as tobe not overlapped with the substrate 705 and the stage 707.

Consequently, the doping apparatus of the present embodiment isconfigured as described above, so that the variations in abundance ratioof the various kinds of ions to be generated by the ion source aresuppressed, while allowing the dropping process with a highreproductivity to adjust the concentration of high accuracy impurityelements.

Next, a doping method using such a dripping device 702 will be describedwith reference to the device shown in FIG. 7.

At first, impurities in the inside of the ion source 701 and the insideof the doping 702 are removed by exhausting in a high vacuum.

The substrates (the target materials) to be subjected to the dopingprocessing are transferred from the road rock chamber 703 and are thenbrought in the waiting chamber 704 in order. Subsequently, eachsubstrate is transferred into the doping chamber through the transfermeans 706 and arranged in place on the stage when a preparation for thedoping processing is completed. The transfer means 706 has a double armstructure. That is, when the preceding substrate is in the dopingchamber, one of the arms pulls out the substrate from the doping chamberwhile the other arm transfers a subsequent substrate into the dopingchamber 702.

When the substrate is brought in the doping chamber 702, thepredetermined material gas is supplied through the gas-supplying system719. In the case of doping phosphorus, phosphorus gas diluted withhydrogen is used. In the case of doping boron, diboron diluted withhydrogen is used. The direct current is applied on the filament whilethe pressures of the ion source 701 and the doping chamber 702 aremaintained at constant by adjusting the amount of material gas to besupplied and the exhaust velocity of the exhausting means. Consequently,plasma is generated in the ion source 701. Then, the material gas isdecomposed by the plasma, generating a plurality of ion species. Thegenerated ion species can be accelerated by applying a predetermineddirect current voltage on the drawer electrode 712 and the acceleratorelectrode 713 to irradiate the accelerated ions on the substrate placedon the stage 707 to allow the doping processing.

At the time of the doping, the measurement of an ion current value forknowing the dose amount is carried out by the ion detector.

In the ion detector, the ion detector 720 for measuring the ion currentvalue at the predetermined monitoring position is mounted in the iondetector.

In addition, the ion current value of the specific ion contained in theion beam at the time of doping is measured by the ion detector (the EXBseparation detector) 722 integrally formed with the EXB separator.

For obtaining the dose amount at the position of the substrate to bedoped, there is the need of measuring the ion current value using theion detector 721 previously arranged at the substrate position (theprocessing position).

Consequently, monitor signals based on the ion current values measuredon the respective ion detectors (720 to 722) before or during the dopingprocessing are transferred to the control means 725. In the controlmeans 725, in addition to the monitor signals, the data processingdescribed in Embodiment 1 or 2 is performed on the basis of data enteredthrough the input means 726 and the memory means 727 to determine thepresence or absence of the continuation of the doping processing.

When the termination of the doping processing is determined in thecontrol means 725, a control signal based on the termination istransferred to the dose amount control system 729 of the dopingapparatus to complete the doping processing. In addition, when thecontinuation of the doping processing is determined in the control means725, a control signal based on the continuation is transferred to thedose amount control system 729 of the doping apparatus to allow thecontinuation of the doping processing.

Furthermore, when the doping is completed by the dose amount controlsystem 729, the electric power application on the filament, and thetermination of the supply of material gas, the termination of ironirradiation, and so on are carried out.

Then, the doped substrate is collected from the doping chamber 702through the transfer means, completing a series of the processing.

According to such a process, the data measured by the ion detectors (720to 721) can be fed back to perform the doping, so that a high accuracyion-doping processing can be realized.

In addition, in the case of performing the doping using the method asdescribed above, for instance a channel doping for controlling thethreshold voltage of the TFT, the control of a sufficient dose amountbecomes possible even though the concentration of the impurity to bedoped into the semiconductor film is in the range of about 1×10¹⁵ to5×10¹⁷ atoms/cm³.

Adapting the configuration of the present invention, the dose amount canbe precisely measured and the dose amount can be adjusted on the basisof the measured data, allowing a stable doping process. Furthermore,making TFT using the doping apparatus having such a control systemallows the realization of stable transistor characteristics.

1. A doping apparatus comprising: a doping processing system having ameans for discharging an ion beam constructed of a plurality of ionspecies, wherein the ion beam includes one conductive type impurityelement; an ion detecting means having a mass separator for measuring anion current value of an ion having the maximum abundance ratio among theplurality of the ion species; a memory means for memorizing a conveningdata associating a concentration of the one conductive type impurityelement in the target material and the ion current value of the ionhaving the maximum abundance ratio; and a control means for calculatingan actual dose amount of the one conductive type impurity element basedon the ion current value of the ion having the maximum abundance ratioand the convening data, and controlling the doping processing system. 2.The doping apparatus according to claim 1, wherein the one conductivetype impurity element is boron, and the ion having the maximum abundanceratio is a hydrogen ion.
 3. The doping apparatus according to claim 2,wherein the hydrogen ion is one of H⁺, H₂ ⁺, and H₃ ⁺.
 4. The dopingapparatus according to claim 1, wherein the ion detecting meanscomprises: a first ion detector for measuring a first ion current valueat a position where a target material is placed; and a second iondetector for measuring a second ion current value at a monitoringposition.
 5. A doping apparatus comprising: a doping processing systemhaving a means for discharging an ion beam constructed of a plurality ofion species, wherein the ion beam includes one conductive type impurityelement and a specific ion; an ion detecting means having a massseparator for measuring an ion current value of the specific ion; amemory means for memorizing a converting associating a concentration ofthe one conductive type impurity element in the target material and theion current value of the specific ion; and a control means forcalculating an actual dose amount of the one conductive type impurityelement based on the ion current value of the specific ion and theconverting data, and controlling the doping processing system.
 6. Thedoping apparatus according to claim 5, wherein the one conductive typeimpurity element is boron, and the specific ion is a hydrogen ion. 7.The doping apparatus according to claim 6, wherein the hydrogen ion isone of H⁺, H₂ ⁺, and H₃ ⁺.
 8. The doping apparatus according to claim 5,wherein the ion detecting means comprises: a first ion detector formeasuring a first ion current value at a position where a targetmaterial is placed; and a second ion detector for measuring a second ioncurrent value at a monitoring position.
 9. A doping apparatuscomprising: a doping processing system having a means for discharging anion beam constructed of a plurality of ion species, wherein the ion beamincludes one conductive type impurity element; an ion detecting meanshaving a mass separator for measuring an ion current value of an ionhaving the maximum abundance ratio among the plurality of the ionspecies; and a control means for calculating an actual dose amount ofthe one conductive type impurity element based on the ion current valueof the ion having the maximum abundance ratio, and controlling thedoping processing system.
 10. The doping apparatus according to claim 9,wherein the one conductive type impurity element is boron, and the ionhaving the maximum abundance ratio is a hydrogen ion.
 11. The dopingapparatus according to claim 10, wherein the hydrogen ion is one of H⁺,H₂ ⁺, and H₃ ⁺).
 12. The doping apparatus according to claim 9, whereinthe ion detecting means comprises: a first ion detector for measuring afirst ion current value at a position where a target material is placed;and a second ion detector for measuring a second ion current value at amonitoring position.